The present invention relates to a tunnel boring machine, i.e. a machine which bores the tunnel without the use of explosives.
During boring with a tunnel boring machine the boring head is pressed against the tunnel front with a large force at the same time as it is rotated. In order to take up the resulting reaction forces during the boring one relies on the tunnel wall. This is done so that a part of the machine is fixed relative to the tunnel wall. In a prior art tunnel boring machine the fixed part comprises a rectangular channel in which a long rectangular beam is movable to-and-fro. This beam carries at one end a bearing housing for the boring head and at the other end a gear box and a number of driving motors which, via a shaft journalled in the rectangular beam, drive the boring head. The boring head is pressed against the tunnel front by means of a number of hydraulic cylinders which are arranged between the gear case and the part fixed relative to the tunnel wall. The reaction moment arising during boring is thus transferred via the rectangular beam and the fixed part to the tunnel wall. Also the axial reaction force is transferred that way.